InstallingWe provide Lightning for Windows, Linux and Mac OS X in a variety of languages. Windows users must have Windows XP or later. Mac OS X users need to use MAC OS X 10.4 or later.

IMPORTANT: Install the updated timezones for Windows XP or later. Information on obtaining the updated timezones can be found in Microsoft Knowledge Base article 955839. Not updating your Windows timezones will result in unreliable and erroneous display and entry of time data! Be sure to do this!

Lightning runs as an extension for Mozilla Thunderbird 3.1.x. Thunderbird 2.0.0.x or 3.0.x is no longer supported. Please use the earlier 1.0b1 (Thunderbird 3.0.x) or 0.9 (Thunderbird 2.0.0.x) release if you still use an earlier version of Thunderbird.

If you are using Seamonkey, please also use the older Lightning 1.0b1. This release doesn't support Seamonkey, but the next release will likely do so again.

In Mozilla Thunderbird, under the "Tools" menu, open the "Add-ons Manager"

Click the "Install" button, locate and select the .XPI file you downloaded in step 1, and click "OK"

Restart Mozilla Thunderbird

Known IssuesThis list covers the major known issues with Lightning 1.0 beta2. Please read this list before reporting any new bugs.

All Systems

Lightning 1.0 beta2 will attempt to guess your timezone on startup. As this is only a best guess, you must manually set the timezone in the Thunderbird Preferences/Options dialog before entering data. Not doing so may cause events to appear at the wrong time

The experimental support for viewing remote calendars offline has various known issues in the area of performance and calendar data display. It does not support the offline editing of events and tasks

It is impossible to load several calendars with different passwords on the same server. (bug 247486)

"By weekday" and "by day" recurrence types (such as "recur on the last weekday of the month") are not supported. (bug 322458)

There are interoperability issues with versions of the DAViCal (RSCDS) CalDAV server prior to release 0.9.5. People using earlier releases of DAViCal are advised to stay with Lightning 0.8 until they can upgrade their DAViCal installation to the current version. (bug 448453)

Lightning 1.0 beta1 is the latest stable release built for Thunderbird 3 and SeaMonkey 2 and contains nearly 500 bugfixes and improvements over the 0.9 release, that improve the add-on's stability, performance and memory consumption.

What's New in Lightning 1.0 beta1Lightning 1.0 beta1 is the latest release of our calendar extension for Mozilla Thunderbird®. We recommend that all users upgrade to this latest version.

The following features have been added to Lightning 1.0 beta1:

Seamless integration into the new Thunderbird 3.0 user interface

The different modes (calendar view, task view) are now diplayed in tabs

Lightning now supports SeaMonkey 2.0 as a host application

You can now define multiple alarms for a single event

CalDAV support and interoperability with various CalDAV servers has been improved

The application stability, performance and memory consumption has been improved

Release Date: January 12, 2010

InstallingWe provide Lightning for Windows, Linux and Mac OS X in a variety of languages. Windows users must have Windows XP or later. Mac OS X users need to use MAC OS X 10.4 or later.

IMPORTANT: Install the updated timezones for Windows XP or later. Information on obtaining the updated timezones can be found in Microsoft Knowledge Base article 955839. Not updating your Windows timezones will result in unreliable and erroneous display and entry of time data! Be sure to do this!

Lightning runs as an extension for Mozilla Thunderbird 3.0.x. Thunderbird 2.0.0.x is no longer supported. Please use the earlier 0.9 release if you are still a user of Thunderbird 2.0.

In Mozilla Thunderbird, under the "Tools" menu, open the "Add-ons Manager"

Click the "Install" button, locate and select the .XPI file you downloaded in step 1, and click "OK"

Restart Mozilla Thunderbird

Known IssuesThis list covers the major known issues with Lightning 1.0 beta1. Please read this list before reporting any new bugs.

All Systems

Lightning 1.0 beta1 will attempt to guess your timezone on startup. As this is only a best guess, you must manually set the timezone in the Thunderbird Preferences/Options dialog before entering data. Not doing so may cause events to appear at the wrong time

The experimental support for viewing remote calendars offline has various known issues in the area of performance and calendar data display. It does not support the offline editing of events and tasks

It is impossible to load several calendars with different passwords on the same server. (bug 247486)

"By weekday" and "by day" recurrence types (such as "recur on the last weekday of the month") are not supported. (bug 322458)

There are interoperability issues with versions of the DAViCal (RSCDS) CalDAV server prior to release 0.9.5. People using earlier releases of DAViCal are advised to stay with Lightning 0.8 until they can upgrade their DAViCal installation to the current version. (bug 448453)

* New icon set and reworked menu structure that only offers the user those options that are currently available to him in calendar or task mode

* Lightning now contains an event list (also known as "unifinder"), which allows the easy selection and sorting of current, future and past events. The unifinder can be easily enabled or disabled by using the "Find events" button on the Calendar toolbar

* Category colors are now shown next to an event box, giving users a much better overview of their differently categorized events

* Events with alarms now have a visual indicator showing an alarm bell

* A totally overhauled alarm dialog

* Easy conversion of mails, events and tasks into each other. The mode toolbar icons on the left side now function as drop targets, which allows you to convert an e-mail to an event or tasks (or vice versa), just by dragging an e-mail to the calendar icon on the left

* Visual overhaul for the today pane

* Lightning now recognizes the timezone definitions in .ics files created by other applications. This fixes the longstanding issue of Lightning miscalculating the date or time of events contained in those files

* The timezone guessing has been significantly improved

* Lightning now contains experimental support for viewing remote calendars offline. This feature has known bugs and is included for testing purposes only

* Lightning contains several performance fixes, which should improve working with larger calendar files

* You can now define for each of your calendars, whether you want to be notified of alarms for events in these calendars or not

* Special builds with support for Sun Java Calendar Server (lightning-WCAP) are no longer available as the base extension package now contains all the necessary code

* Thunderbird 1.5.0.x builds are no longer supported. Users of Thunderbird 1.5.0.x are strongly encouraged to update to Thunderbird 2. Please use the "Check for Updates..." option in the help menu to get the update

This add-on is not compatible with your version of SeaMonkey because of the following:

Version 0.5
Released June 27, 2007
2.0 MB
Works with
Thunderbird 1.5 - 2.0.0.*

Much more polished user interface in the calendar viewsEvent invitations can be sent and received via iMIP/iTIP (Lightning only)Working hours are backAutomatic migration of data in Sunbird 0.2, iCal.app, and EvolutionMuch improved printing functionalityBetter integration of Lightning into Mozilla Thunderbird (Printing, Undo/redo, Copy/paste)Support for Google Calendar (via the Google Calendar Provider extension)and much more. A full list of changes that have gone into this release can be found on The Rumbling Edge weblog.